Many machines include one or more components that move relative to one another. Some such machines include a position-sensing system with a single sensor element that generates a signal related to proximity of the sensor element to some portion of one of the components between which relative motion occurs. For example, a position-sensing system may have a single sensor element that generates a signal related to proximity of the sensor element to some projection of the component, such as a gear tooth. The machine may use the signal from the sensor element as an indication of the positional relationship between the components.
Unfortunately, a number of factors may cause significant variation in the relationship between the proximity of the sensor element to the component and the value of the signal generated by the sensor element. For example, temperature variations, variations in the characteristics of the sensor element, and variations in the characteristics of electricity supplied to the sensor element may all increase or decrease the sensor signal value. Because of variation in such parameters, a position-sensing system employing a single sensor element may indicate the positional relationship between components with undesirably low precision for some applications.
U.S. Pat. No. 6,988,421 to Tokumoto (“the '421 patent”) discloses a position-sensing system that uses two sensor elements to determine the rotational position of a gear. Each of the two sensor elements sits radially outward of the teeth of the gear. The gear is constructed of magnetic material. As the gear rotates adjacent the sensor elements, the gear teeth pass the sensor elements, and the sensor elements sense the density of the magnetic flux generated by the gear. Thus, the value of the signal generated by each sensor element cycles up and down as the gear teeth pass the sensor element, thereby providing an indication of the position of the gear relative to the sensor elements.
The '421 patent discloses that the position of the gear and the signal from each sensor element may have a nonlinear relationship in certain ranges. To address this, the '421 patent discloses positioning the two sensor elements so that their sensor signals are out of phase by an amount that prevents the nonlinear operating ranges of both sensor elements occurring at the same time. Thus, at all times, at least one of the sensor elements provides a sensor signal linearly related to the position of the gear.
Although the rotary position-sensing system of the '421 patent uses two sensor elements to sense the position of the gear, certain disadvantages persist. For example, while using two sensor elements positioned as disclosed in the '421 patent addresses nonlinear operating ranges of the sensor elements, it does not address variations in operating parameters that may change the value of both sensor signals. Additionally, in some applications it may prove impractical or imprudent to construct the sensed component out of magnetic material and sense the magnetic flux generated by the sensed component, as disclosed by the '421 patent.
The position-sensing system and methods of the present disclosure solve one or more of the problems set forth above.